The proposed research will examine changes in attitudes and fertility-related behaviors (including sexual practices, number of sexual partners, and contraceptive use) that have resulted from the fear of contracting Acquired Immune Deficiency Syndrome (AIDS) and other sexually transmitted diseases (STDs) among a nationally representative sample of women aged 20-35, in the United States. In addition, we will explore the interrelationships between knowledge about STDs, attitudes towards both STDs and behavior that is associated with STDs, and fertility-related behavior, using as conceptual frameworks models such as the Health Belief Model and the Subjective Expected Utility Model. Two samples are proposed for the data collection: (1) a follow-up, in 1989, of women who were initially interviewed in 1983 when they were 20-29 years of age (the National Survey of Unmarried Women). In 1983, detailed baseline information was collected from these women about their sexual, contraceptive, pregnancy and birth histories, as well as their attitudes towards fertility-related behavior. In 1989, these women will be 26-35 years of age. Follow-up information will enable us to observe changes in these women's attitudes and behaviors since AIDs has become a health threat. We expect to be able to reinterview 920 of the original sample of 1,314 women. (2) a new nationally representative sample of 20-25 year-old women (both married and unmarried). This new panel is advantageous because it will enable us to study the knowledge, attitudes, and behavior of women 20-35, which almost completely covers the age range of women who are most at risk of contracting AIDS, and it will allow us to make comparisons between groups of women so that period, cohort, and age effects can be determined. For this sample, 700 interviews are expected to be completed. Both samples will include over-samples of black women, who are disproportionately represented among persons who have been diagnosed with AIDS. As soon as it is feasible, a public use data tape will be made available, so that the broader research community can provide timely analysis of issues not covered by this research proposal.